121 lines
3.2 KiB
Python
121 lines
3.2 KiB
Python
# -*- coding: utf-8 -*-
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'''
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TRXD PDU definitions based on declarative codec.
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'''
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# TRX Toolkit
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#
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# (C) 2021 by sysmocom - s.f.m.c. GmbH <info@sysmocom.de>
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# Author: Vadim Yanitskiy <vyanitskiy@sysmocom.de>
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#
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# All Rights Reserved
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License along
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# with this program; if not, write to the Free Software Foundation, Inc.,
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# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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import codec
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class Header(codec.BitFieldSet):
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''' Header constructor for TRXD PDUs. '''
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def __init__(self, ver: int):
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codec.BitFieldSet.__init__(self, len=1, set=(
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codec.BitField('ver', bl=4, val=ver),
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codec.BitField.Pad(bl=1), # RFU
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codec.BitField('tn', bl=3),
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))
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class MTS(codec.BitFieldSet):
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''' Modulation and Training Sequence. '''
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DEF_LEN = 1
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STRUCT = (
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codec.BitField('nope', bl=1),
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codec.BitField('mod', bl=4),
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codec.BitField('tsc', bl=3),
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)
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@staticmethod
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def get_burst_len(mod: int) -> int:
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''' Get burst length by modulation type. '''
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GMSK_BURST_LEN = 148
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if (mod >> 2) in (0b00, 0b11): # GMSK or AQPSK
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return 1 * GMSK_BURST_LEN
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elif (mod >> 1) == 0b010: # 8-PSK
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return 3 * GMSK_BURST_LEN
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elif (mod >> 1) == 0b100: # 16QAM
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return 4 * GMSK_BURST_LEN
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elif (mod >> 1) == 0b101: # 32QAM
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return 5 * GMSK_BURST_LEN
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elif mod == 0b0110: # GMSK (Access Burst)
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return 1 * GMSK_BURST_LEN
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raise ValueError('Unknown modulation type')
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class BurstBits(codec.Buf):
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''' Soft-/hard-bits with variable length. '''
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def __init__(self, name: str, *args, **kw):
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codec.Buf.__init__(self, name, *args, **kw)
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# This field has a variable length that depends on moduletion type
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self.get_len = lambda v, _: MTS.get_burst_len(v['mod'])
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# This field is not present in NOPE / IDLE indications
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self.get_pres = lambda v: not v['nope']
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class PDUv0Rx(codec.Envelope):
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STRUCT = (
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Header(ver=0),
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codec.Uint32BE('fn'),
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codec.Uint('rssi', mult=-1),
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codec.Int16BE('toa256'),
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codec.Buf('soft-bits'),
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codec.Buf('pad'), # Optional
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)
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def __init__(self, *args, **kw):
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codec.Envelope.__init__(self, *args, **kw)
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# Field 'soft-bits' is either 148 (GMSK) or 444 (8-PSK) octets long
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self.STRUCT[-2].get_len = lambda _, data: 444 if len(data) > 148 else 148
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class PDUv0Tx(codec.Envelope):
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STRUCT = (
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Header(ver=0),
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codec.Uint32BE('fn'),
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codec.Uint('pwr'),
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codec.Buf('hard-bits'),
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)
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class PDUv1Rx(codec.Envelope):
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STRUCT = (
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Header(ver=1),
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codec.Uint32BE('fn'),
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codec.Uint('rssi', mult=-1),
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codec.Int16BE('toa256'),
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MTS(),
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codec.Int16BE('cir'),
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BurstBits('soft-bits'),
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)
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class PDUv1Tx(PDUv0Tx):
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# Same structure as PDUv0Tx, only the version is different
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def __init__(self, *args, **kw):
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PDUv0Tx.__init__(self, *args, **kw)
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self.STRUCT[0]._fields[0].val = 1
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